Androgenic processes in diploid potato (2n=2x=24) were studied in three interspecific hybrids. Five incubation temperature treatments were examined. Temperature shock (35°C) during the first 12 h of anther culture and elevated incubation temperature (30°C 16h/20°C 8h) (hereafter 35°C-30°C/20°C) enhanced androgenic embryo production. Variation among experiment dates was highly significant. Temperature treatment (35°C-30°C/20°C) during anther culture did not influence the subsequent conversion rate of androgenic embryos, thus providing a simple and effective way to enhance androgenic embryo yield. Repeated experiments were conducted to study extended anther culture by replacing anthers into medium following the usual harvest 6 weeks after culture initiation. Embryos continued to be produced after the first harvest. Embryo yield at the first harvest was significantly correlated with that at the second harvest (P <0.01). Significantly more embryos were produced when anthers were put back into the same medium compared to fresh medium in extended anther culture. Although relatively high embryo yield was produced in extended anther culture, high contamination and low regeneration rate eliminate any practical use unless a better regeneration protocol is developed. Randomly amplified polymorphic DNA (RAPD) techniques were applied to analyze the genetic composition of anther-derived plants, whose ploidy level was predetermined by flow cytometry. The RAPD fragments amplified from various anther derived diploid plants (2n=2x=24) were compared with those from anther donor (2n=2x=24) and anther-derived monoploids (2n=1x=12). Anther donor and anther-derived monoploids were distinguished by scoring segregating bands as well as total number of scorable bands that exhibited polymorphism. Thus RAPD has the potential to separate homozygous from heterozygous diploids, since the frequency of RAPDs present in homozygous diploids is expected to be the same as in a group of known monoploids, whereas heterozygous ones will be similar to the anther donor. / Master of Science

Potato (Solanum tuberosum L.) cultivars Atlantic, BelRus, Kennebec, Superior, and Yukon Gold, grown at six locations in Southwest Virginia, were analyzed for yield, percent dry weight, specific gravity, soluble protein, and ascorbic acid. Thereafter. tubers were cold stored at 3 C for six weeks, reconditioned at 25 C for two weeks, and analyzed for percent dry weight, specific gravity, soluble protein, and ascorbic acid. Potato grown in one location was analyzed for glucose, fructose, sucrose, and total sugars. Another experiment was conducted to evaluate the effect of seed type and in-row spacing on yield and quality of Yukon Gold. Cultivar and location influenced yield and quality of potato at harvest, after cold storage, and following reconditioning. Kennebec, Atlantic, and Yukon Gold produced higher yield of US No. 1 tubers than Superior and BelRus. Atlantic and BelRus had higher percent dry weight and specific gravity than the other cultivars. Specific gravity increased during cold storage and following reconditioning. Percent dry weight increased during reconditioning but did not change during cold storage. / Master of Science

Competence for leaf disc regeneration, anther culture, and protoplast culture was tested in the parental, F₁, and F₂ generations of a diploid cultivated primitive potato, S. phureja (2n=2x=24). The parental pair consisted of AM3-8, an anther culture derived homozygous diploid, and NBP2, a heterozygous, field selected line. AM3-8 produced embryos in anther culture, and shoots on cultured leaf discs, but its cells did not divide after protoplast isolation. Cells of NBP2 divided to form calli and shoots in protoplast culture, but the clone did not respond to anther culture or leaf disc regeneration. All the individual plants in the F₁ generation were responsive to both anther culture and protoplast culture; however, there was segregation for the ability to regenerate shoots from leaf discs. The F₂ population, the result of a sib-cross, segregated for all three tissue culture competencies. Segregation data fit a one gene model for anther culture competence with the homozygous dominant genotype expressing the highest response, the heterozygous resulting in a marginal response, and the homozygous recessive resulting in no response. A two-gene model applied to the protoplast culture data, with a dominant allele at both loci required for division to occur after protoplast isolation. Leaf disc regeneration data could only be explained by a two gene model with recessive alleles at each locus required for the highest response, a dominant allele at either of the loci resulting in a marginal response, and dominant alleles at both loci resulting in no response. No significant correlation was found among these traits, implying three separate genetic mechanisms which segregate independently. Several temperature regimes were used in an attempt to enhance caulogenesis following protoplast isolation during the p-callus growth and regeneration phase of a single F₂ clone from this S. phureja population. Each of eight treatments was applied to 120 p-calli in six replications of 20 each. Shoot regeneration was scored at 94, 105, 121, and 131 days after protoplast isolation. P-calli cultured at 30°C days and 20°C nights produced significantly more shoots than those cultured at a constant 25°C. Therefore, the standard 25°C used for p-calli regeneration in potato may not be optimal; elevated temperatures or simply a diurnal temperature fluctuation may enhance morphogenesis. / Master of Science

Inheritance of androgenetic competence was studied in 10 diploid potato species hybrids and 16 backcross progeny. Ten hybrid families including three reciprocals were generated between competent clones of S. phureja and incompetent clones of S. berthaultii, S. microdontum and S. phureja. The F₁ hybrid families segregated for androgenetic competence with some highly competent and some incompetent genotypes in all families. The expression of androgenetic competence was modified by parents lacking competence. The cytoplasm of species lacking competence exerted a greater influence on the expression of androgenesis in intraspecific than in interspecific hybrids. The segregation data of 16 backcross progeny between a highly competent hybrid and its incompetent parent suggested that competence may be under control of a single dominant gene. Androgenetic competence can be transferred among sexually compatible potato species. The transfer of desirable traits to a monoploid background can be expected using an- drogenetically competent selections in hybrid combination with germplasm expressing the desired attributes. In an attempt to determine genetic changes of regenerated potato plants following anther and callus cultures, 20 callilines of two S. phureja clones were examined. Four of 20 callilines selected for fertility and diploidy were morphologically indistinguishable among themselves and from the parental clone that had not undergone a tissue culture cycle. Even though morphologically indistinct from the parental clone, all four callilines exhibited higher seed set as pollen parents in 4x-2x crosses and two of the four exhibited higher recombination frequency between the centromere and the y gene. The estimated increase in map distance of the y locus ranged from 3.4 to 10.0 units. Progeny analysis revealed no significant morphological differences among 4x-2x hybrid families under field conditions, and only a single difference among 2x-2x hybrid families under screenhouse conditions. Hence, variation induced in tissue culture may have occurred without detectable morphological change. Assuming no adverse tissue culture effects, breakage of undesirable linkage groups may be an advantage of caulogenesis before backcrossing. / Ph. D.

Call number: LD2668 .T4 1953 R3 / Master of Science

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

No description available.

Call number: LD2668 .T4 1950 P5 / Master of Science

Thesis--PlanA (M.S.)--University of Wisconsin--Stout, 2000. / Includes bibliographical references.

Late blight of potato incited by Phytophthora infestans (Mont.) de Bary, is one of the plant diseases particularly well suited for fundamental studies on the physiology of parasitism. For this reason, and also because of its economic importance, this disease has been the object of numerous and diverse investigations. However, it is only recently that studies on the biochemistry of the alterations resulting from infection, and of disease resistance and susceptibility, have been initiated. [...]